Retractable soot blower of the long travel type



Aug. 4, 1959 w. F. CANTIERI RETBAC-TABLE SOOT BLOWER OF' THE LONG TRAVEL TYPE 4 Sheets-Sheet 1 Filed Nov. 19. 1954 Aug. 4, 1959 w. F. CANTIERI 2,897,532

RETRACTABLE sooT BLQWER oF THE LONG TRAVEL TYPE Filed Nov. 19. 1954 4 sheets-sheet 2 I N VEN TOR. V//zam Z4 Cdrfzz'erz' BY ZW L? ,yr #Ng/sf Aug- 4 l959 w. F. CANTIERI 2,897,532

RETRACTABLE som1 BLOWER oF THE LONG TRAVEL TYPE Filed Nov. 19. 1954 A 4 Sheets-Sheet 3 All@ 4 1959 w. F. CANTIERI 2,897,532

RETRACTABLE sooT BLowER oF THE LONG TRAVEL TYPE Filed Nov. 19. 1954 4 sheets-sheet 4 72 l[Ha/[40 L@ Ta FNK/S,

nn'rnAcrALn' soor Browan or rim LoNG TRAVEL TYPE William F. Cantieri, Lancaster, (Ehio, assignor to Diamond Power Specialty Corporation, Lancaster, Ohio, a corporation of Ohio Application November 19, 1954, Serial No. 469,908

6 Claims. (Cl. 155-317) The present invention relates to the construction of cleaning devices of the type particularly adapted to clean the heat exchanging surfaces of large industrial and public utility boilers and the like.

In cleaning the heat exchanging surfaces in the hotter portions of large boilers, retractable cleaning devices or soot blowers of the long travel type are commonly used. Such soot blowers are usually constructed with a slidable lance tube which is arranged to be projected through the wall of the boiler into the interior of the boiler setting and adapted to discharge a suitable fluid such as steam or air against the heat exchanging surfaces of the boiler. The lance tube is adapted to be retracted to a position outside the boiler setting when not in use to protect it against the damaging effects of the high temperatures normally present in the boiler. An important object of the present invention is to provide an improved retractable soot blower of the long travel type incorporating improved supporting means and which is compact and rugged in construction and which may be disposed outside of the building containing the boiler or other like heat exchanging apparatus to which the soot blower is appurtenant.

A further object is to provide a novel truss construction for a retractable soot blower of the long travel type which permits mounting of the blower mechanism inside of a structure practically no longer than that which is now required for a much shorter travel blower.

Another object is to provide such a blower having a rigid lance tube which is so supported and constructed that it is capable of longer unsupported travel than the lance tubes of prior art blowers of this general class.

Another object is to provide a stepped blower lance tube for a soot blower of the indicated character which may be projected into a boiler setting with a smaller amount of deflection than with the present one-piece construction type of blower lance tube.

Still another object is to provide improved supplemental supporting means preventing sagging of certain portions of such a blower of the long travel type, and which is of simple and reliable character and fully automatic in its operation.

Still another object is to provide an improved cleaning apparatus of the indicated character wherein the blow valve controlling the blowing medium inlet is controlled by improved fully automatic regulating mechamsm.

Other objects, features and advantages of the present invention will become apparent from the present disclosure.

In the drawings:

Figure 1 is a broken elevational view of a retractable soot blower of the long travel type constructed in accordance with the present invention;

Fig. 2 is a fragmentary, diametric longitudinal sectional view, of the outer end portion of the blower lance `tube assembly;

Fig. 3 is an elevational view of the structure illustrated 2,897,532 Patented Aug. 4, 1959 2 in Fig. l, looking in the direction of the arrow 3 of Fig.` 1 and on a somewhat larger scale;

Fig. 4 is a sectional view of the structure illustrated in Fig. l, on a somewhat larger scale, taken along line 4 4 thereof;

Fig. 5 is a partial sectional view of the structure illustrated in Fig. 4, taken along the line 5 5 thereof;

Fig. 6 is a sectional view of the structure illustrated in Fig. 4, taken along the line 6 6 thereof;

Fig. 7 is a sectional view of the structure illustrated in Fig 1, but on a somewhat larger scale, taken along the line 7 7 thereof;

Fig. 8 is a longitudinal Vertical sectional elevational view, partially broken away to show different planes of section, of the feed tube traveling support;

Fig. 9 is a broken, diametric longitudinal sectional view of the stepped blower lance tube of the invention;

Fig. l() is a fragmentary, broken, longitudinal sectional elevational view of the rear portion of the structure illustrated in Fig. 1, on a somewhat larger scale, taken from the side and showing the automatic regulating mechanism for the blow valve;

Fig. ll is a plan view of the structure illustrated in Fig. 10;

Fig. 12 is a fragmentary side elevational View of a portion of the structure illustrated in Fig. 1, on a somewhat larger scale and partially broken away, showing the automatic latching mechanism for releasably connecting the blower lance tube carriage with the feed tube traveling support carriage;

Fig. 13 is a fragmentary, diametric longitudinal sectional view of the outer end portion of a modified blower lance tube assembly provided with pellet feeding and projecting means; and

Fig. 14 is a fragmentary elevational view of the inlet end of a blower structure corresponding generally to Fig. l, but modified to provide pellet input means coacting with the modified lance tube of Fig. 13.

Referring now to the drawings, reference character 10l designates generally a truss assembly which form the principal supporting structure and track means lfor guiding the projection and retraction of the lance tube 12 of my improved retractable soot blower of the longtravel type. The truss assembly 10 is rigidly carried by a suitable supporting structure including hanger means 11 and the boiler wall 14. As shown in Fig. l, the soot blower is installed so that the left end of the truss assembly 10 is adjacent to the outside of the wall 14 of the boiler setting. The truss assembly 10 extends outwardly from the boiler wall 14 while the lance tube 12 is projectible inwardly through the boiler wall 14, which it enters through a suitable wall box, as shown at 16. The lance tube 12 is movable from the retracted position, in which it is shown in Fig. l, and in which it lies entirely outside the high temperature zones, to an extended position within the boiler setting. The lance tube 12 has a smooth exterior, of cylindrical form, and carries a suitable nozzle on the forward end thereof, such as is designated in Fig. 2 by numeral 13, through which steam, air, or a combination of these, or other desirable cleaning fluids may be projected against the boiler tubes or other heat exchanging surfaces to be cleaned.

My improved soot blower truss assembly 10 is adapted to form a supporting means which permits mounting of a blower mechanism inside of the truss struct-ure which is little longer than the lance tube itself. The truss assembly 10 comprises an upper pair of laterally spaced, longitudinally extending angle irons 38 and 40 and a lower pair of laterally spaced, longitudinally extending angle irons 42 and 44 rigidly joined by a plurality of longitudinally spaced vertical channels as 46 and longitudinally spaced horizontal channels as 48. The sides of the truss assembly are provided with a plurality of stilfening members 50, preferably angle irons, which are diagonally disposed on the sides of the truss assem-A bly. The front and rear ends of the truss assembly V10 are enclosed by the cover plates 52 and 54, respectively, which are suitably secured to the truss assemblyas by the bolts 56. The sides of the truss assembly 10 may be enclosed, if desired, with a metal screening material as shown at l57. Fixedly secured tothe front cover plate 52, as by the bolts 58, is a stuffing box 59 interconnected with the wall box 16, and provided with packing means (not shown) operatively associated withthe lance tube 12 ton provide a suitable seal between the interior of the boiler setting and the atmosphere. Fixed to the front cover plate 52, as by welding, is a supporting bracket 60 hingedly connected at 62 to a yoke member 64 whch is adapted to lit around the inner end of the wall box 16.

The lance tube 12 is rotated and driven longitudinally by a driving mechanism contained Within the carriage 'generally designated 1S, which is connected to and moves with the rear en d of the lance tube. The rear end of the lance tube 12 is supported in the lower forward portion ofthe carriage 18 by suitable fastening means, described in detail hereinafter. As is best seen in Fig. 9, the lance tube 12 has a stepped inner diameter and is preferably made from a plurality of intertted sections which are of the same external diameter but of graduated internal diameter, suitably secured together in endto-end relation, as by welding, and arranged with progressively decreasing wall thicknesses towards the nozzle end of the lance tube. This internally stepped lance tube construction permitsincreased lance tube projection travel with less deflection than occurs with a lconventional lance tube of the same overall length having uniform wall thickness. Although the stepped lance tube 12 is illustrated as having three sections, namely: rear section 24, middle section 26 and front section 28, it will be understood that any other number ofsections may be used as may be found desirable in each particular case.

The lance tube driving carriage 18, which is described in detail hereinafter, is rollably supported in a track assembly formed by the longitudinally disposed angle irons 38, 40, 42 and 44 of the truss assembly 10.

A motor base plate 66 is fixedly secured to the truss assembly, preferably on the upper side, near the forward end thereof by any suitable means, as by'welding. Securely mounted on the base plate v66, as bythe bolts 68, is a suitable reversible drive electric motor 70, having a pulley 72 suitably secured on the forward end lof the shaft 73, and adapted to drive an Octagon drive tube 74 by means of the belt 76, and the pulley 78 which is mounted on the forward end of the Octagon drive tube 74. The octagon drive tube 74 is rotatably mounted in the truss assembly 10 as by means of the bearing assemblies 80 and 82 which are disposed on the front and rear cover plates 52 and 54, respectively.

As is best seen in Figs. 4 and 5, the Octagon drive tube 74 is slidably connected to the lance tube carriage 18 by means of the drive tube sleeve assembly 84 which is internally shaped to telescopically receive the drive tube 74. The sleeve 84 is driven `,by the octagon drive tube 74 and is slidable thereon. The sleeve 84 is xed in the forward end of the rotatable tubular shaft 86 which is suitably supported and longitudinally disposed in the carriage 18, as by the bearing assemblies 8S and A90. The tubular shft 86 isprovided with an annular shoulder 92 disposed towards the rearward end thereof. A ydriving spur gear 94 is xedly held on the rearward end of the tubular shaft 86 by any suitable means, as by keying, and is disposed so as to abutl againstthe annular shoulder 92. The driving spur gear 94 meshes with a driven spur gear 96, xedly held on a tubular rotatable shaft 98, which is suitably supported inthe lance tube 'carriage 18, as by means of the bearing assemblies and 101. As is best seen in Fig. 6, the tubular shaft 98 is adapted to slidably receive and fixedly hold therein the rear section of the stepped lance tube 12. The lance tube 12 is held in the tubular shaft 98 by means of suitable bolts as 102, mounted in thelance tube ange 20 and which threadably engage the flange 104 which is mounted on the forward end of the tubular shaft 98. Y

As is best seen in Fig. 6, a worm shaft 106 is longitudinally rotatably mounted in the lance tube carriage 18, adjacent the drive shaft 74, by suitable bearing assemblies as 108 and 110. Fixedly held on the Worm yshaft 106 on the rearward end thereof, is a driven spur gear 112 adapted to meshably engage the driving spur gear 94 on the octagonal drive tube 74. A driving worm 114 is xed on the front end of the worm shaft 106 by any suitable means, as by keying, and is axially positioned on the worm shaft 106 by means of the gear spacer 116 and annular shoulder 118. As is best seen in Fig. 4, a worm gear shaft 120 is transversely disposed in the lance tube carriage 18 above the worm shaft 106 and is rotatably carried therein by means of suitable bearing assemblies as 122, 124 and the |bushing 126. A driven worm 'gear 128 is iixedly held on one end of the worm gear shaft 120, as by keying, and isada'pted to meshably engage the driving worm 114. A driving spur gear 13,0 is xed on the other end of the worm gear shaft 120 and is centrally disposed -in the lance tube carriage 18 'so as `to mesh with lthe longitudinally disposed gear rack 132 Vwhich is fixed on the upper side of the truss assembly 10, as by welding.

The lance tube carriage 18 is rollably supported in the'truss assembly 10 by two upper and two lower roller brackets as 136, on which are mounted suitable vvertical rollers as 138. The vertical rollers 138 may be journaled on shaft'portions which are eccentric 'with respect toth'e supporting portions 140 by which their shaft portions are mounted in the brackets 136, which permits the rollers to be vertically adjusted. The roller'brackets 136 are provided with horizontal side rollers, as 142, which are adapted to abut the vertical portions of the aforementioned angle irons and coactwith the vertical rollers 138 to position the lance tube carriagelS in the truss vassembly 10. The vertical and horizontal side rollers `'may be provided with suitable grease fittings as shown at Y139.

As is best seen in Fig. l, a feed tube '144, through which the blowing medium is fed into the interior of the lance tube 12, projects into the lance tube through a suitablestuiiing Ibox, as 146, which is carried by and disposed at the rear end of the lance tube carriage 18. The stufhng box 146 is adapted to engage and be rigidly held upon the threaded rear end 147 of the `lance tube 12. Feed tube 144 is 4long enough so lthat the forward end thereof remains within the lance tube 12 when the latter is fully extended, the forward end of .the 4feed tube144 being open so l'that the Vblo'wing medium is freely discharged into the interior of the lance tube 12 for delivery to and discharge from the blowing nozzle 13.

As is best seen in Figs. 1, 3, 10 and ll, the rearend of the feed tube 144 is provided with a 'poppet-type blow valve 148 which' is adapted to be opened and closed Vby the forward andrearwar'd movement, respectively, Iof the larice'tube carriage 18. The valve148is provided on the upper side thereof with a pivotally mounted lever 150 which is provided 'with a forwardly extending'arm 154. The arm 154 is pivotally attached at 156 to the upper end of the Valve stem 158. A `forwardly extending actuating lever 153 is pivotally lconnected to the lever 150 asby the clevis 155 and pins 157 and 159. The Iforward end of the actuating lever 153 is' pivotallyW Aconnected to a cam lever as by the cap screw 162. :Fixedly secured, as'by welding, to the top of the truss assembly 10 is a transverse plate 164 in which is rigidly held a vertical bearing post 166 adapted to journal la pivot sha-ft 168 "which carries on the lower end thereof the cam lever 160. A rearwardly extending cam trip bar 170 is secured to the upper side of the lance tube carriage 18, as by the cap 'screws 172, and is provided on the rearward end thereof with a depending portion 174 adapted to slidably engage the slot 176 in the cam lever 160 upon movement of the lcarriage 18.

As is best seen in Figs. 1, 7, 8 and I12, there is provided a traveling carriage or support 180 for the feed tube 144- which is rollably supported in the truss assembly 10 'and which functions so that when the lance tube 12 is extended, the traveling support carriage will `be disposed :approximately midway between the lfront cover plate 52 fand the rear cover plate 54 of the truss `assembly 10, to prevent sagging of the feed tube 144. The traveling support carriage 180 includes a pair of spaced, vertical iside plates 182 and 184 mounted on suitable upper and lower roller brackets, as 186, which yare rollably supported in the Vangle iron track of the truss assembly 10, as by the vertical rollers 188. The traveling support carriage 180 is provided with a transversely disposed feed ,tube roller shaft 190 on which is centrally mounted an antifriction feed tube roller 192 adapted to continuously engage and support the feed tube 144. Fixed between the spaced side plates 182 and 1184 -are a pair of transversely disposed vertical plates 194 and 196 which are adapted `t-o rigidly support the drive tube support collarI `198 in which the octagon drive tube 74 is s'lidably mounted. The traveling support carriage 180 may be provided with side rollers, las at 200. rThe vertical rollers 188 may be mounted on eccentric shafts, as shown at 202, to provide for vertical adjustment of the rollers. The vertical and side rollers may be provided with suitable grease fittings, as shown at 204.

Carried by the traveling support carriage 180 is a pair of forwardly extending brackets 206 and 208 fixed on the spaced side plates 182 and 184 as by cap screws 210. The outer, end of the brackets 206 yand 208 carry a transverse lhorizontal latch shaft 212 therebetween, suitably secured thereto as by the washers 213 and cotter pins 215. As is best seen in Fig. 12, the lance tube carriage 18 is provided with a pair of rearwardly extending brackets as 214 which are fastened to the sides of the carriage 18, as by cap screws 216. Rotatably mounted in the rear end of the brackets 214 is a transverse horizontal axle 218. A pair of latchpieces 220 and 222 are mounted on the axle 218 and secured thereto as by means of cap screws 224. The rear end of each of the latchpieces 220 and 222 is provided with a hooked end portion, as 226, which is adapted to engage the transverse latch shaft 212 on the traveling support 180. The axle 218 carries a downwardly extending arm 228 secured thereto yas by the set screw 230. The lower end of the arm 228 carries a pivotally mounted depending7 linger 232 adapted to be pivoted forwardly but restrained from pivoting rear,- wardly by the depending arm portion 234. When the lance tube carriage 18 moves Iforwardly, the cam lug 236, which is rigidly secured in a suitable position on the lower angle iron 44, is adapted to engage the pivotally mounted finger 232 to actuate the arm 228 and accoudingly the latchpieces 220 and 222 upwardly so as to `disengage the hooked end portions 226 from the latch shaft 212. On the return movement of the carriage 18, the latchpieces 220 and 222, being heavier than the arm 228, will be in a down or horizontal position `and the hooked end portions 226 of the latchpieces will engage the latch shaft 212 and, the traveling support 180 will be carried backwardly to the rear end of the truss assembly 10 to the position shown in Fig. l. During such return movement, the pivotally mounted finger 232 will pivot forwardly and override the cam lug 236.

As is best seen in Figs. 13 and 14, the retractable soot blower of the present invention may be provided, if desired, with suitable pellet delivery and projecting means. The inlet end of the blowing fluid feed tube 144 is modi- 6 ed toperniit xial projection thereinto from the rear of :a pellet feed tube 241. This may be accomplished by providing the feed tube 144 with a suitable inlet T, as 240, through which the pellet feed tube 241 extends uninterruptedly. The pellet feed tube is smaller than the I.D. of the T and iiuid feed tube 144, however, so that it does not interfere with the iiow of blowing fluid. The pellet feed tube 241 telescopically overengages Aa pellet delivery -tube 242 fixed in the lance tube and slidable in the feed tube during movements of the lance tube. The pellet delivery tube is shaped to have a discharge portion 244 secured adjacent and coaxial with but spaced from. the nozzle outlets 246. The discharge portion 244 may be curved to insure :accurate projection of the pellets through the nozzle outlets 246 and .against the heating surfaces of the boiler, but the gap 247 between the outlet end of pellet discharge portion 244 and the inner end of the blower nozzle 246 permits discharge of blowing fluid from within the lance tube through the same nozzle. In operation, with the soot blower in the retracted position as shown in Fig. l, when the drive motor 70 is energized, the drive tube 74 is rotated by means of the drive pulley 72 and the belt 76 driving the pulley 78. The rotating drive tube 74 drives the sleeve 84, which in turn fdrives the tubular shaft 86 and the spur gear 94. The

lance tube 12 -is rotated by means: of the spur gear 94 driving the spur gear 96, which, in turn, drives the tubular :shaft 98, in which the lance tube 12 is nested. The lance tube 12 is moved longitudinally by means of the spur gear 94 driving the spur gear 112, which is mounted on the worm shaft 106 carrying the worm 114. The worm Gili 114 drives the worm gear 128 which :is mounted on the worm gear shaft 120, carrying the spur gear 130. The spur gear 138 meshably engages the longitudinal rack 132 and drives the lance tube carriage 18 and lance tube 12 in a longitudinal direction determined by the direction of rotation of drive motor 70. As is best seen in Fig. l, at the start of a projecting movement, the feed tube traveling support carriage 180` is connected to the lance tube carriage 18 by means of the latchpieces 220` and 222 which are then hooked over the latch shaft 212. When the l-ance tube carriage 18 reaches an intermediate position in its travel in the truss assembly 10, it will be seen that the linger 232 will abut the cam lug 236, thereby pivoting the latchpieces 220y and 222 upwardly and disengaging them from the latch shaft 212 on the traveling support 180. On the return movement of the lance tube carriage 18, the hooked end portions 226 will override and engage the latch shaft 212 and carry the feed tube traveling support 188 back to the retracted position as shown in Fig. 1.

When the blower is fully retracted, the automatic regulating mechanism for controlling the blowing medium inlet valve 148 will be arranged in the position shown in Fig. 11. As the lance tube carriage 18 moves forwardly to extend the lance tube 12, the depending p0rtion 174 is carried forwardly `and engages the slot 176 in the cam lever 160. Continued forward movement of the carriage 18 causes the cam lever 160 to be pivoted to the dot-dash line position as designated by the numeral 160". It will be seen that as the cam lever 160 pivots to position 160', the lever 153 will be actuated forwardly and the llever 150 will follow accordingly thereby forcing the valve stem 158 downwardly to the open position. On the return or rearward movement of the carriage 18, the depending portion 174 will engage the cam lever at the position and return it to the position as shown by the full lines in Fig. 11. It will be seen that the return movement of the. cam lever 160 actuates the levers 153 `and 150 backwardly so as to move the valve stem 158 upwardly to the closed position.

While it will be apparent that the preferred embodiments of the invention herein disclosed are well calculated to fulll the objects above stated, it will be appre- 7 ciated `that the invention is susceptible to modification, variation and change without departing from the proper scope'or fair meaning of the subjoinedv claims.

I rclaim:

1. In a soot blower construction of the Ilong Vtra-vel type, a generally tubular hollow stationary supporting truss adapted yto be mounted appurtenant and substantially perpendicular to the wall -of a .boiler setting or the like, a lance tube mounted in said Itruss 'for'longitudinal movement into and from the same and to positions of varying projection therefrom, said lance tube being substantially smaller than said truss, adriving carriage longitudinally movably mounted in and guided by said truss and connected -to said lance tube, to actuate the latter, said lance tube also being rotatable in said truss, a motor, means drivable by the motor and also carried by said truss for moving the carriage fand lance tube longitudinally and for rotating said lance tube with respect to said carriage and truss, including a-drive shaft journaled in the truss and kextending parallel to the lance tube and to the path of movementvof the carriage, and power transmission means insaid carriage having a single torque input portion slidably keyed on said shaft and rotatably drivable thereby, Ysaid transmission having two power output portions, one such output portion reacting longitudinally against -said truss to move said carriage and lance tube longitudinally, and the other such `output portion reacting angularly upon the lance tube to rotate the latter.

2. In a long retracting-soot blower construction, a hollow tubular truss assembly of rectangular cross section having longitudinal angle irons defining the corners thereof, a lance tube of materially smaller cross section than and longitudinally movable into and outwardly of the truss, a carriage rollable within the truss and having supporting and guiding wheels engaging said angle irons, said-lance tube'being connected to and -longitudinally driva'ble by said carriage, means for propelling the carriage to'move the lance tube longitudinally, and means carried at least partly by lthe carriage for rotating the lance tube.

, 3. A slidably extensible and retractable soot blower construction adapted for cleaning the heating surfaces of a boiler or the like comprising a hollow tubular truss structure 'forming a `longitudinally lextending `track assembly,means for `mounting said truss with a forward end adjacent to a boiler wall and projecting outwardly therefrom, a lance tube longitudinally slidable in said truss structure to and from a position in which it projects substantially outwardly from said forward end and-having a rearend within Ysaid-truss structure, means appurtenant to said forward end of the truss structure slidably supporting said lance tube, a driving carriage supported in said track assembly and movable forwardly and backwardly Vtherein and connected to the rear end of said lance tube, means for actuating said carriage, and thereby also actuating the lance tube forwardly and backwardly in saidtrack assembly while simultaneously rotating said lance tube, a longitudinally disposed cleaning fluid feed tube having the rear end thereof supportedby said truss and having a part thereof projecting toward said forward end ofthe truss structureand telescopically received in the rear end of said lance tube, and a traveling feed tube supportcarriage located to the rear of the driving carriage and movable with respect to the feed tube from a supporting position at atpoint near the rearA end of'the feed tube when the lance tube is in a retracted position to a point nearer the forward endof the feed tube when the" lance tube is in ,an extended position.

v4. A slidably extensible and retractable soot blower construction as defined in claim 3, wherein said traveling feed tube support carriage comprises a frame rollably supported in said track assembly, a roller on said frame engaging `the feed tube to support the same, releasable latch means for separably connecting said traveling feed tube support carriage to said lance tube carriage, and means responsive to movement of the traveling feed tube support carriage from a position near the rear end of the feed tube to a point nearer the forward end of the feed tube for releasing said latch means.

5. A slidably extensible and retractable soot blower construction adapted for cleaning the heating surfaces of a boiler or the like comprising, a first pair of laterally spaced longitudinally extending upper track members, a second Vpair of laterally spaced horizontally extending lower ,track members disposed below said upper track members, a plurality of parts interconnecting said track members and securing them rigidly together to form a hollow tubular truss, means for mounting said truss with a forward end adjacent to a boiler wall and projecting outwardly therefrom, a lance tube longitudinally slidable in said trussto and from a position in which it projects substantially ,outwardly from said forward end and having a rear end within said truss, means appurtenant to said forward end of the truss slidably support-ing said lance tube, a carriage supported and positioned in said truss and movable forwardly and backwardly in the truss and connected to the rear end of said jlance tube, means for actuating said carriage and lance tube forwardly and backwardly in said truss while simultaneously rotating said lance tube, a feed tube telescopically interitted with the rear end of and projecting rearwardly from and adapted to feed a cleaning uid into said lance tube, a traveling feed tube support carriage also supported and positioned in said truss movable with respect to the feed tube and engageable with said feed tube to support the same at a position forward of the rear end of the latter when the lance tube is in an extended position, and releasable latch means for separably `connecting said traveling support carriage with said first-,mentioned carriage.

6. In a .construction as defined in claim 3, latch-type coupling means for releasably interconnecting said two carriages, latch tripping means carried by the truss structure and effective in response .to movement of the driving carriage in a forward direction beyond a predetermined position to release said latch-type coupling means, whereby the driving carriage may continue forwardly toward a boiler wali while the support carriage remains in an intermediate position, said coupling means being re- `latched in response to rearward movement of the driving carriage beyond said position, the support carriage beingdrivable in both directions by the driving carriage when the coupling means is so latched.

References Cited in the le of this patent UNTED STATES PATENTS 1,664,865 Snow Apr. 3, 1928 2,339,327 Fox Jan. 18, 1944 2,351,117 Glinn et al. June 13, 1944 2,583,726 Chalom Ian. 29, 1952 2,611,455 Woods Sept. 23, 1952 2,668,978 DeMart Feb. 16, 1954 2,696,631 Hibner et al Dec. 14, 1954 2,710,225 Richards June 7, 1955 2,760,222, Anderson Aug. 28, 1956 FOREIGN PATENTS 453,205 Great Britain Sept. 7, 1956 1,026,751 France Feb. 11, 1953 

